352
FXUS63 KGRB 051941
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
241 PM CDT Sat Jul 5 2025

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Scattered thunderstorms this afternoon and evening across the
  region. Isolated severe storms are possible that could produce
  damaging wind gusts. Torrential rainfall is also possible that
  could produce localized urban and low-lying flooding. The most
  favored time frame for strong storms is through 9 pm.

- Until storms arrive later today, it will remain very warm and
  humid with heat indices in the lower to middle 90s over east-
  central to northeast Wisconsin. Those with outdoor plans should
  take precautions for the heat.

- Gusty winds and high waves will lead to conditions hazardous to
  small craft through tonight on the Lake Michigan nearshore
  waters. Small craft should exercise caution on the Bay of Green
  Bay. Hazardous swimming conditions will also be present for the
  Lake Michigan beaches across Door, Kewaunee, and Manitowoc
  counties through tonight.

&&

.DISCUSSION...
Issued at 230 PM CDT Sat Jul 5 2025

Short Term...Tonight and Sunday

Shortwave trough crosses upper Great Lakes through tonight,
dragging a sfc cold front across the state late this evening
through the overnight hours. Strongest wave within the trough is
remnant MCV that is shifting over western Upper Michigan with tail
end of the MCV helping to kick off convection over northwest into
central and north-central WI. Though SBCAPEs have increased to
1500-2500J/kg, stronger effective shear over 30 kts staying ahead
of MCV to the north has limited storm organization thus far over
our area. However, still a risk of isolated severe storms rest of
the afternoon and into the evening given the instability and
solar insolation that has occurred so far today, especially over
east-entral and far northeast WI. PWATs near 2" with slower
effective storm motions will result in brief torrential downpours.
Where individual cells train, there will be a risk of isolated
flooding, especially if the heavy rain occurs in low-lying and
poor drainage areas. Ahead of the storms, heat index values will
remain in the mid to upper 90s, maximized across portions of the
Fox Valley and just to the west. Showers and storms will end late
evening and overnight as winds turn north.

Lingering clouds will partially clear out late tonight into Sunday
morning. Not near as warm and turning less humid behind the front.
Highs reaching the mid 70s to lower 80s, warmest across portions
of central WI. Will be a bit breezy behind the front along the Lake
Michigan shore, but winds and waves look to come up short to justify
the need for additional beach hazard statements. Those heading out
on the water should still expect choppy conditions.

Long Term...Sunday Night Through Saturday

Relatively seasonal weather can be expected during the upcoming
week. Low amplitude, zonal flow will be present across the US-
Canadian border which will send shortwave impulses across the
region on Monday night/Tuesday and also towards Friday. These
will be the time frames of higher shower and thunderstorm
chances. The potential for severe weather appears low at this
time. There are some hints that shortwave troughs crossing during
these times could be stronger. If that is the case and they time
out during peak heating, then severe weather chances would
increase.

Seasonable temperatures are forecast next week. Highs on most
days will range from the upper 70s to middle 80s. Lows each
night will range from the middle 50s to middle 60s.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1216 PM CDT Sat Jul 5 2025

Showers and a few thunderstorms are spreading into central and
north-central WI well ahead of a cold front back over MN. Bulk of
these will be done for these areas 22z-24z. Elsewhere, isolated
showers are just starting to form, but expect these to become
more widespread in coverage, peaking in coverage and intensity
between 20z-02z. Continue to highlight greatest chances for
thunder at all terminals using TEMPO groups. Confidence was not
high enough to go with prevailing TSRA at this time and also
didn`t include any higher gusts. If needed, these details can be
included in future amendments. Once the main period of showers and
storms ends later this evening, expect lower stratus to form,
perhaps down to lower MVFR. Eventually as north winds freshen late
tonight, clouds will slowly scatter out and lift to VFR.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement through late tonight for WIZ022-040-050.
&&

$$

DISCUSSION.....JLA/MPC
AVIATION.......JLA